Why are there advertisements on all my browsers?

[wolf]

Whenever I open a browser like Internet Explorer, Mozilla Firefox, or even Google Chrome, there are advertisements everywhere! And the thing is is that they pop up on websites that never had advertisements! Whenever I go on Tumblr and other websites, now there's advertisements never there before and it's bothering me! I'm not sure how they got there, but now I have to use Opera because everything has advertisements. When I used adblock, they just added more ads! I don't know what to do and it's really bothering me. I want to use these browsers, but I need to know how to get rid of the ads first. Can someone please help?

[pessi]

sound like your computer is infected by some adware / malware.

Consider to install spybot on your computer and scan it for once and remove any adwares.

http://www.safer-networking.org/private/

[CoreyBryant]

ESET has a Stand-alone Malware Removal Tools that you can run If you do not have a AV program, I do recommend their ESET Smart Security 7

Otherwise Comodo has a lot of free tools to check out

Also go to Control Panel - Programs - do you see any programs you do not recognize? Did this just start happening? You can click on the row that says date installed if that might help.